Spleen cells from Mr1-1pr mice gradually develop a loss of CD4+ T helper cell function that is age-dependent which is concomitant with the appearance of anti-DNA antibodies and of suppressor cells that selectively suppress only CD4+ T helper cell function. These suppressor cells were found to be T lymphocytes of the L3T4 phenotype. This observation contrasts with Mr1 +/+ mice that exhibit none of the above during the same time period. Twelve of fifteen human patients with SLE exhibit a similar selective loss of CD4 T helper cell function.